We investigate the coalescence of massive black hole (MBH≥ 106M⊙) binaries (MBHBs) at 6 < z < 10 by adopting a suite of cosmological hydrodynamical simulations of galaxy formation, zoomed-in on biased (>3σ) overdense regions (Mh~ 1012M⊙dark matter haloes at z = 6) of the Universe. We first analyse the impact of different resolutions and AGN feedback prescriptions on the merger rate, assuming instantaneous mergers. Then, we compute the halo bias correction factor due to the overdense simulated region. Oursimulations predict merger ratesthat range between 3 and 15 yr-1 at z ~6, depending on the run considered, and after correcting for a bias factor of ~20-30. For our fiducial model, we further consider the effect of delay in the MBHB coalescence due to dynamical friction. We find that 83 per cent of MBHBs will merge within the Hubble time, and 21 per cent within 1 Gyr, namely the age of the Universe at z > 6. We finally compute the expected properties of the gravitational wave (GW) signals and find the fraction of LISA detectable events with high signal-to-noise ratio (SNR > 5) to range between 66 per cent and 69 per cent. However, identifying the electro-magnetic counterpart of these events remains challenging due to the poor LISA sky localization that, for the loudest signals (Mc~ 106M⊙at z = 6), is around 10 deg2.

Probing z ≥ six massive black holes with gravitational waves

Chakraborty, Srija
;
Gallerani, Simona;Zana, Tommaso;Valentini, Milena;Di Mascia, Fabio;Vito, Fabio;Barai, Paramita
2023

Abstract

We investigate the coalescence of massive black hole (MBH≥ 106M⊙) binaries (MBHBs) at 6 < z < 10 by adopting a suite of cosmological hydrodynamical simulations of galaxy formation, zoomed-in on biased (>3σ) overdense regions (Mh~ 1012M⊙dark matter haloes at z = 6) of the Universe. We first analyse the impact of different resolutions and AGN feedback prescriptions on the merger rate, assuming instantaneous mergers. Then, we compute the halo bias correction factor due to the overdense simulated region. Oursimulations predict merger ratesthat range between 3 and 15 yr-1 at z ~6, depending on the run considered, and after correcting for a bias factor of ~20-30. For our fiducial model, we further consider the effect of delay in the MBHB coalescence due to dynamical friction. We find that 83 per cent of MBHBs will merge within the Hubble time, and 21 per cent within 1 Gyr, namely the age of the Universe at z > 6. We finally compute the expected properties of the gravitational wave (GW) signals and find the fraction of LISA detectable events with high signal-to-noise ratio (SNR > 5) to range between 66 per cent and 69 per cent. However, identifying the electro-magnetic counterpart of these events remains challenging due to the poor LISA sky localization that, for the loudest signals (Mc~ 106M⊙at z = 6), is around 10 deg2.
2023
Settore FIS/05 - Astronomia e Astrofisica
galaxies: high-redshift; gravitational waves; quasars: supermassive black holes
   Binary massive black hole astrophysics
   B Massive
   European Commission
   Horizon 2020 Framework Programme
   818691
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11384/141024
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